1. Field of the Invention
The present invention relates to a nitride semiconductor laser device incorporating a nitride semiconductor laser chip using a nitride-based compound.
2. Description of Related Art
Nitride semiconductors are materials that can emit light in a short-wavelength band including the ultraviolet to green region. In recent years, blue-violet semiconductor lasers have been developed particularly eagerly using such materials. For example, Patent Publication 1 discloses an example of a nitride semiconductor laser device.
FIG. 7A is a perspective view of a semiconductor laser device, with the cap thereof removed to show the structure inside, and FIG. 7B is a perspective view of the exterior appearance of the semiconductor laser. A semiconductor laser chip 1003 is mounted on a metal stem 1001 so that heat is efficiently dissipated to the stem 1001. An electrode (for example, a p-electrode) on the top face of the semiconductor laser chip 1003 is electrically connected, via a wire, to a pin (bar-shaped electrical terminal) 1004 fixed to the stem 1001. On the other hand, an electrode (for example, an n-electrode) on the bottom face of the semiconductor laser chip 1003 is electrically connected to the stem 1001 itself. The stem 1001 itself is electrically connected to another pin 1005. The pin 1004 is fixed to the stem 1001, but is insulated from the stem 1001 itself.
In this structure, when an electric current is fed between the pins 1004 and 1005, the current is fed to the semiconductor laser chip 1003, which thus carries out laser oscillation. As shown in FIG. 7B, the semiconductor laser chip 1003 and the wire are protected by being enclosed in a metal cap 1006. The cap 1006 has formed therein a window 107 through which to extract laser light.
It has been found that a semiconductor laser device using a nitride semiconductor laser chip 1003, like the one described above, is vulnerable, in particular, to a surge. A nitride semiconductor laser chip 1003 readily deteriorates when exposed to a surge as may be applied to the chip via a supply voltage line during the process for evaluating the characteristics of a semiconductor laser device, or when exposed to static electricity (which, for the sake of convenience, is also dealt with as a kind of surge in the present specification) that may be applied to the chip accidentally in the fabrication line for fabricating an end product incorporating a semiconductor laser device as a light source.